1. Field of the Invention
The present invention relates to a solar cell, and more particularly, to a solar cell including a microlens for improving light capture property and a method of fabricating the solar cell.
2. Discussion of the Related Art
In general, a solar cell, which is a semiconductor device converting a solar energy into an electric energy, includes a junction of a positive (P) type semiconductor and a negative (N) type semiconductor and has the same basic structure as a diode. Most typical solar cells have a structure of a positive-negative (PN) junction semiconductor layer where a P type semiconductor layer and an N type semiconductor layer between facing two electrodes.
For the purpose of improving photoelectric efficiency, the solar cell includes a light collecting means that concentrates the light of the sun and irradiates the light onto the surface of the solar cell. For example, the light collecting means is a microlens.
The microlens is fabricated through various methods such as an etching method using a laser pulse, a reflow method using a photoresist, a dry etching method, a glass surface processing method using carbon dioxide (CO2) laser, a method using a surface tension of a liquefied glass, an ion beam processing method for a polymer by a laser deposition, an inkjet method, a heating method for a photoresist, a gray scale masking method and an embossing molding method.
FIGS. 1A to 1C are cross-sectional views showing a reflow method using a photoresist of fabricating a microlens according to the related art. In FIG. 1A, a resin layer 20 for a microlens is formed on a substrate 10 and a photo mask 90 is disposed over the resin layer 20. The resin layer 20 is patterned through a photolithographic process including exposure and development steps to become a resin pattern 25 corresponding to a curved surface of a lens as shown in FIG. 1B. In FIG. 1C, the resin pattern 25 (of FIG. 1B) is heated and reflows in a heat treatment apparatus to become a microlens 30.
However, the method of fabricating a microlens according to the related art is performed through a photolithographic process in which a plurality of steps such as a photoresist coating step, an exposure step and a development step are required. Specifically, the exposure step requires an expensive photo mask and an expensive exposure apparatus. As a result, a microlens according to the related art is fabricated through complicated steps with a high fabrication cost.